Isomerization of paraffins in the presence of nascent aluminum halide and a heterocyclic compound



July 29, 1947. c. G. MYERS Er AL 2,424,953

ISOHERIZATION OF PARAFFINS IN THE PRESENCE 0F NASCENT ALUIINU HALIDE AND A HETEROCYCLIC COHPOUND 3 'Sheets-Sheet 3 Filed Juno 30, 1945 w fo INVENTORS Patented July 29, i947 ISOMERIZATION i PRESENCE F NASCENT ALUMINUM l HETEROCYCLIC COM- HALmE AND a POUND Claude G. Myers, Bryn Mawr, Pa., and Rowland C. Hansford and Alexander N. Sachanen, Woodbury, N. I., asaignors to Socony-Vacuum' Oil Company, Incorporated, a corporation of New York Application .rune so, 1945, sei-ui No, 602,440

(on. zoo-asses) l 12 Claims.

This invention relates to the catalytic isomerization of hydrocarbons, and is more particularly concerned with an improved process for isomerizing parailnic hydrocarbons having ve to seven carbon atoms.

As is lWell known to those familiar with the art, compounds are said to be isomeric when they are composed( of the same chemical elements in thevsame proportionby Weight, but have difierent properties. Such compounds are referred to as isomers, and the reaction conditions of temperature, time, etc., of processes that eifect the transformation ofV one isomer into another, accordingly called isomerization processes, are broadly referred toas isomerizing orA isomerization reaction conditions. Structural isomerism is one type of isomerism and connotes that which involves compounds having the same empirical formulas andidenti'cal molecular formulas, but which have different structural formulas, and, consequently, diierent properties. Structural isomerism is referred to as chain isomerisxn when the isomerism is due to diierent arrangements of the carbon atoms in the carbon chain. Butane and 2methyl propane or isobutane are typical examples of chain isomerlsm.

The production of`isoparafnic, or branchedchain parafiinic hydrocarbons, from the corresponding normal orstraight-chain paramnic hydrocarbons, andl of more highly branched-chain parainnic hydrocarbons from branched-chain' parai'linic hydrocarbons is highly desirable because of the generally higher anti-knock ratings of the branched-chain paralnlc hydrocarbons. The branched-chain parafflnic hydrocarbons. generally, are also more reactive than the corre- I spending normal hydrocarbons, and, therefore,

they are widely utilized in alkylation processes for the formation of alkylates comprising highlybranched paraflinic hydrocarbons boiling within the gasoline boiling range. Furthermore, isoparaflinic hydrocarbons, like isobutane, may be dehydrogenated to the corresponding isobutenes and these may be polymerized and subsequently hydrogenated to produce saturated motor fuels of high octane ratings.

ever, the ever increasing demand for high quality aviation gasoline has necessitated the discovery of additional sources of isoparamnic hydrocarbons. Isomerization processes, whereby normal "or straight-chain parafllriic hydrocarbons, the

sources of which are plentiful, are converted into isoparaiilnic or branched-chain paraillnic h'ydro-` l carbonsconstitute one of the most important sources of isoparalinic hydrocarbons now av'ail-V able.` e

Accordingly, numerous processes have been proposed for eiecting the transformation of normal paraillnic hydrocarbons into isoparainic hydrocarbons. Ordinarily, these processes comprise the use of substances that facilitate the isomerination conversion, consequently referred toln the art as lisomerlzation catalysts. Some` of these isomerization processes employ, in addition to an isomerization catalyst, substances that in- ',f

crease theisomerlzationcatalytic activity of the catalyst, hence called promoters. More recently, it has been discovered that in addition to the promoter, it is advantageous to carry out the catalytic isomerization operation in the presence of added quantities of other substances.

Although most of the so-called acid" type catalysts, such as aluminum chloride, boron triuoride, sulfuric acid, ferric'chloride, zinc chlooxide, of hydrogen halide, and water, of hydrated Originally, the xed gases obtained around petroleum refineries constituted an adequate supu ply of isoparaillnic hydrocarbons suitable for inorganic salts, of preformed solutions of an aluminum halide in hydrogen chloride which has been liquiiied under pressure, and of compounds of the syp' R-soion wherein a is either the hydroxyl group or a halogen, as isomerization catalysts. In some instances, the use of inert carriers in conjunction with aluminum halides with or without hydrogen halide promoters has also been suggested.

In the isomerization of normal butane, un-

alkylation and polymerization operations. Howmodified aluminum halides with or without hy- The use of rin the isomerization of the higher homologues of normal butane causes undesirable additional reactions, including cracking which may be followed by alkylation, henceforth referred to, in the interest of brevity, as side reactions, resulting in substantial yields of butanes and of hydrocarbons having molecular Weights higher than those of the charge stocks. It is well known that aluminum halides react with hydrocarbons to .produce complex masses spoken of in the art as -sludges." These "sludges have been :found to be considerably less active as cracking catalysts than the aluminum halides themselves; hence, it has been proposed to use sludges preformed by the treatment of naphthas with aluminum halides, by the treatment of cyclohexene with aluminum halides, by the treatment of alkyl aromatics with aluminum halides, or to use a preformed double compound of aluminum halide-alkyl aromatic-alkyl halide. However, the use of these f'sludges, although reducing the undesirable side reactions, does not completely inhibit them.' Accordingly, in isomerization operations involving'the use of aluminum halides, it has been suggested to use so-called cracking inhibitors. Hydrogen used per se or in conjunction with propane, and metallic aluminum have been proposed as cracking inhibitors.

The formation of aluminum halide catalysts in situ is a very recent development in the catalytic isomerization of normal butane and its higher homologues. In these processes, the catalyst is produced in situ by the reaction of metallic aluminum in the form of chips, foil, ilakes, grindings, etc., with a halogen or a compound capable o f chemically reacting as the equivalent of a. free halogen under the isomerization reaction conditions. Examples of these compounds are hydrogen halides, alkyl halides, organic acid halides, and mixtures thereof. Metallic aluminum in comminuted form may be placed in the reaction zone to form a stationary bed or a series of stationary beds through which the charge stock flows, or small amounts of comminuted metallic aluminum may be added to the charge stock and thereby carried into the reaction zone. If desired, small amounts of substances such as hydrogen chloride, that expedite the formation of Friedel-Crafts catalysts, as well as small amounts of water, may be advantageously used, as is well known in the art. The halogen or halogen-containing compound may be introduced directly into the reaction zone in the case where the comminuted metallic aluminum is placed therein prior to the isomerization operation, or the halogen or halogen-containing compound may be added to th'e charge stock in the case where the comminuted metallic aluminum is added to the charge stock.

Nevertheless, the processes of the prior art have never been entirely successful in inhibiting the undesirable side reactions that occur in the isomerization of hydrocarbons having ve to seven carbon atoms.

A copending application, Serial Number 554,184, iiled September l5, 1944, is directed to the process for eilecting the isomerization of paraffinic hydrocarbons having ve to seven carbon atoms inclusive, whichv comprises contacting said hydrocarbons in a reaction zone under isomerization reaction conditions, with a nascent aluminum halide isomerization catalyst formed in said reaction zone under said isomerization reaction conditions, in the presence of an organic aromatic compound. In accordance with the process set forth in thiscopendng application, undesirable side reactions that occur in the isomerization `oi paraninic hydrocarbons having iive to seven carbon atoms are practically completely eliminated.

We have now discovered that these side reactions of cracking and alkylation likewise may be practically completely eliminated if the activity, as a cracking catalyst, of the aluminum halide catalyst in statu nascondi is inhibited by the incorporation in the charge of small amounts of certain types of organic heterocyclic compounds. Under such conditions, the aluminum halide catalyst may be said to have specific isomerizing activity.

We have found that in the isomerization of paraillnic hydrocarbons having ve to seven carbon atoms inclusive, in the presence of aluminum halide isomerization catalysts, it is possible to inhibit substantially completely undesirable side reactions including cracking and/or alkylation, by carrying out the isomerization operation using nascent aluminum halide-isomerization catalysts formed in situ and in the presence of added, relatively small amounts of certain types of organic heterocyclic compounds.

It is understood that free halogens, hydrogen halides, as well as various organic halogen compounds capable of reacting with metallic aluminum to produce aluminum halides, may be used. From the commercial standpoint, however, the use of hydrogen halides is unquestionably preferable.

Accordingly, it is an object of the present invention to provide an etficient isomerization process. Another object is to provide an eicient process for isomerizing parailinic hydrocarbons having ilve to seven carbon atoms inclusive. A further object is to afford an improved process for isomerizing parainic hydrocarbons having five to seven carbon atoms in the presence of nascent aluminum halide isomerization catalaysts formed in situ. A more specic object is to provide a. process for isomerizing parafnnic hydrocarbons having five to seven carbon atoms inclusive in which undesirable secondary reactions are practically completely inhibited. A very important object is to provide a process capable of carrying out the above objects by using small amounts of certain types of organic heterocyclic compounds.

Other objects and advantages of the present invention will become apparent to those skilled in the art from the following description taken in conjunction with the following drawings, in wh'ich:

Figure l shows a series of curves representing graphically the relationship between the conversion per pass of normal pentane into isopentane and into butane and residue, in the presence of aluminum chloride in statu nascendi, and the concentration of thiophene in the charge;

Figure 2 shows two curves representing graphically the relationship between the conversion per pass of normal pentane into isopentane in the presence of aluminum chloride, preformed and in statu nascendi, and the concentration of aluminum chloride based onthe pentane charged;

Figure 3 shows two curves representinggraphically the relationship between the conversion per pass of normal pentane into butane andv residue,

in the presence of aluminum chloride, preformed and in statu nascendi, and the concentration of aluminum chloridev based .on the pentane charged;

Figure 4 shows two curves representing graphically the relationship between the total conver'- sion per passof normal pent-,ane into isopentane,

butane and residuein the presence of laluminum chloride, preformed andin statu nascendi, and the concentration ofaluminum chloride basedon the pentane charged; and j Figure ,5 shows two curves representinggraphiy cally the relationship between the conversion of normal pentane into isopentane in the presence of aluminum chloride, preformed and in statu .nas-

cendi, and the concentration of thiophene inthe Broadly stated, the present invention provides a process for electing the isomerizatlon of paraillm'c hydrocarbons having ive to seven` carbon atoms inclusive, whichcomprises contacting said hydrocarbons in a reaction zone under isomerization reactionconditions, with a nascent aluminum halide isomerization catalyst formed in said reaction zone under said isomerization reaction conditions, in the presence of rcertaintypesof organic heterocyclic compounds. y n

It must be clearly understood that when we speak ofv effecting the isomerizationof hydrocarbons, we have reference ,to the conversion of normal parafiinicy hydrocarbons into their iso or branched-chain forms, aswell asethe conversion of isoparaillnic or branchedchainparamnic hydrocarbons into more highly branched forms.

An important feature of ourv invention is that in the isomerization of pentanes and hexanes,

all `undesirable side reactions are 4substantiallyV compieteiyinhibited.

Another feature is that in the isomerization of,

heptanes, theundesirable side reactions are almost completely inhibited.

A further feature is that thealurninum. halide isomerization catalysts are utilized in their highest state-.of catalytic activity. i. e., inthe nascent state, While the undesirable side reactions in' the isornerizationy of pentanes, hexanes, and heptanes are inhibited.

.Generally speaking, the organic heterocyclic.' compounds which we have found to have an in,

hibiting effect upon undesirablesde reactions.

during the isomerization of` hydrocarbons, such as-pentane, hexane, and heptane, in the presence of aluminum halide isomerlzationfcatalysts in statu nescendi, comprise compounds containing an heterocyclic ilve-membered ring 'and compoundsk containing an heterocyclic siX-membered ring. Thiophene, furan, furfuraldehyde, a-pico'- line, pyridine,. piperidine.,` carbazole, pyridine hydrochloride, indole, and quinoline may be menv tioned speciiically by way of non-limiting examples of organic heterocyclic compounds suit#y able for the process of the present invention( It must be noted that these heterocyclic compounds may be used per se or in admixture with diluents not undesirable, provided that the concentration'ofthe heterocyclic compounds is suffi'- ciently high so that the diluents dou-not materially aiTect the reaction, when a sufiicient amount of material is used to achieve the effective heterocyclic compound concentrations.

Referring now more particularly to the curves y' shown in Figure l, which are based on data ob-v tained by treating normal pentane at a temperature of aboutl00 C. for about l hour, usingv 6 charge stocks containing in addition to parts of normal pentane, y16.1 parts -by weight of aluminum, 6.9 partsby weight of dry, gaseous hydrogen chloride, and varying amounts of thiophene, it willbe observed thatin the absenceof thiophene, the catalyst VV causes side reactions of crack-- ing and' alkylation as readilyY as isomerization, so that large amountsoi butanes vand heavy residuel are formed. Uponjthe addition of thiophene, the undesirableside reactions are inhibited, un-

til at a Aconcentration of about 0.5% by weight of-thiophene,` thev undesirable side'reactions are for all practialpurposes`,`-cornp1etely suppressed,`

so that `theisomerization reaction proceedsunhindered, thereby producing high yieldsv oi isopentane. When the concentration of thiophene exceedsV aboi1"tf2.5%v byfweight of the pentane charged, the catalyst isdea'ctivated not only withA respect to the side reactions'l but also with respect to the isomerization reaction, so that substanstially unreactednormal pentaneA is" recovered.

It must be noted, however, that appreciable deactivation of the catalyst, with respect to isomerization, takesjplace when the concentration of thiophene is of the order of about 1.0% by weight. From thecurves of Figure 1, it would appear that fora hydrogen chloride concentration of 6.9 parts by weight, the most practical vthiophene co-ncen'- trations to be used, to insure substantially com;

plete `suppression of undesirable side reactions and concurrent maximum yields of isopentane per pass, lie lin the comparatively narrow range of about 0.5% to about 2.0%. i

y i The range of concentrations necessary to insure substantially completesuppression of undesirable side reactions 'and concurrent v`maximum yields of isomer Yper passof ourfheterocyclie compound inhibitors varies -with each 'compoundn Too large ya concentration-of lany of thev heterocycllc compound inhibitors of'our 'invention will inhibit substantially all reaction. In any particular case, the most desirable concentration of the heterocyclic lcompound inhibitor'to be-used canv be readily ascertained by oneskilled in the art,

the essential desiderata, in accordance withthe' present invention as illustrated by thercurves l shown in Figure l, being a substantially complete suppression of undesirable side reactions with concurrent high vultimate yields of isomer.

When no inhibitors are employed, we-'have found that under comparable conditions, there is substantially little diierence between operations wherein,v aluminum halide" ycataylsts in statu nas/cendi are used, and operations wherein pre-y formed Aaluminum halide catalysts are employed, in so faras the yieldsof isomers andthe amounts of undesirable products produced are concerned.

As illustrated by the curves shown in Figures 2, 3"' and 4, which are based on data obtained by' treat' ing` normalf pentane at Aatemperature of about 100,C for` about 1 hour, in the presence of vary# ing amounts of 'preformed' aluminum chloride and of aluminum lchloride formed in situ, the production of cracked productaof higher boiling hydrocarbons, and of isomerized hydrocarbons is essentially the same irrespective of the catalyst employed. The use of aluminum halides in statu nascendi may be yconsideredj-therefore,` a -convenient method of introducing the catalyst in thereaction'zone. Noess'ential advantage may be claimed for it over the use of preformed aluminum halides, with respect to the results obtained. In each case, curve A is based upon the use of metallic aluminum and'hydrogen chloride, -while curve B is based upon the use of an amount of accesos aluminum chloride approximately equal to that formed in the corresponding run on curve A. The aluminum chloride was activated with hydrogen chloride in amounts that were in excess of that remaining after the formation of aluminum chloride in situ in the corresponding run on curve A.

As has been pointed out by several investigators, the advantage of using small amounts of hydrogen halides (on the order of 1% to 2%) in conjunction with aluminum halides is merely a prolongation of the. 'catalytic activity of the aluminum halide catalysts. Accordingly, the curves shown in Figures 2, 3 and 4, may be considered as evidence that, in so far as isomerlzation reactions areconcemed, aluminium chloride, formed in situ from metallic aluminum and hydrogen chloride, is essentially no better or no worse than an equivalent amount of preformed aluminum chloride.

Referring now more particularlyto the curves shown in Figure 5, which are based on data ob-` tained by treating normal pentane at e. temperature of about 100 C. for about l hour, using charge stocks containing in addition to 100 parts by Weight of normal pentane, 16.1 parts by weight of metallic aluminum, 6.9parts by weight of hydrogen chloride, and varying amounts of thiophene, and amounts oitl aluminum chloride, hydrogen chloride, and thiophene substantially equal to those in the corresponding runs Where metallic aluminum and hydrogen chloride were employed, respectively; it will be observed that under substantially identical isomerizing conditions. the combination of metallic aluminum, hydrogen chloride and thiophene is far more eiective than the combination of aluminum chloride and thiophene even though an amount of preformed aluminum chloride equal to that formed in situ in the first instance, and an amount of hydrogen chloride substantially equal to that remaining after formation of the aluminum chloride in situ, and present as promoter in the rst instance, were used. It is apparent, therefore, that our heterocyclic compound inhibitors partially inhibit the isomerization catalytic activity oi aluminum chloride while substantially. completely inhibiting its cracking and/or alkylation catalytic activity. Our inhibitors suppress the isomerization catalytic activity of aluminum chloride in statu nascondi to a far smaller degree than they inhibit the isomerization catalytic activity of preformed aluminum chloride, While still substantially completely inhibiting its cracking and/or alkylation catalytic activity. Hence-although as illustrated by the curves shown in Figures 2, 3 and 4, there is no particular advantage in the use of metallic aluminum and hydrogen halides in place of preformed aluminum halides, other than one of convenience, there are decided advantages in. accordance with the present invention in the use of metallic aluminum, hydrogen halides, and our heterocyclic compound inhibitors. l

We have not been able to nnd any evidence that in the process of the present invention, other metals, such as iron or zinc, can he used instead of aluminum. Since the isomerization catalytic activity of the halidcs of such metals is considerably less than that of aluminum halides, it is probable that in our type of operation the halides of these metals are formed in amounts insumcient to promote reaction.

The present process is capable of converting normal paramnicrhydrocarbons into their corresponding branched-chain or iso forms, as well as branched-chain paraiiinic or isoparanic hydrocarbons into more highlyy branched forms. The charge stocks may comprise mixtures of two or more normal or branched-chain paraimic hydrocarbons which may contain also small amounts of normal and/or branched-chain olenic hydrocarbons. It should be pointed out, however, that the presence of unsaturates, even in small amounts, deactivates aluminum halide catalysts, and therefore increases considerably catalyst consumption. Generally speaking, any hydrocarbon mixture `comprising normal or branched-chain parafnic hydrocarbons in predominant amounts, is asuitable charge stock for the process of our invention. We have found, however, that 'the eiectiveness oiour heterocyclic compound inhibitors decreases with increasing molecular Weight of the hydrocarbons to be isomeriaed. No inhibitor appears to be necessary in the isomeriaation of normal lontane. Our inhibitors substantially completely suppress cracking and other undesirable side reactions in the isomeriaation of normal pcntane and normal hexane, almost completely suppress undesirable side reactions in the isomerization of normal heptane, and are of little value i in the isomerization of normal octane.

The isomerlzing conditions of the process of the present invention include Wide ranges of temperatures, time of contact, catalyst concentration, pressures, etc., as is Well known in the art. It must be clearly understood, however, that all these factors are more or less inter-related, and that under a given set of conditions, the ease of formation of aluminum halide from metallic aluminum and the halogen-containing substance, will govern to a considerable extent, the temperature and time of reaction. Ordinarily, temperatures varying between about '75 C. and about 200 C., and a contact time varying between about several seconds and about one hour, depending upon the temperature, the pressure and the amounts of hydrogen halide, aluminum, and heterocyclic inhibitor, produce good results.

The isomerization reaction may be carried out in either the liquid phase or in the gaseous phase, depending upon the particular conditions used. We prefer to use a liquid phase operation, the pressureemployed being sufficient to maintain the hydrocarbons as Well as the inhibitor, in the liquid phase at a temperature within the range indicated hereinbefore.

The process may be carried out as a batch, continuous or semi-continuous type of operation. Particularly when the process is conducted on a commercial scale, economic considerations make it advantageous to operate in a. continuous manner. For efficient operation, whether the process is carried out on -a batch or continuous basis, it is essential that the reactants be intimately contacted 'with one another. This may he achieved in several ways and in apparatuses that are weil known in the art.

In accordance with our invention, .We obtain a product containing substantial amounts of branched-chain hydrocarbons which may be separated from the effluent and fractionated to recover the desired isomer or isomers. The unconverted constituents may then be recycled with fresh chargestock, to the isomerization reaction zone for further treatment. .Small amounts of aluminum halide "sludge, of the order of 15% by Weightof hydrocarbon charge, kare formed in the process.I This sludge represents the main source of process loss. If relatively high propor- Y tions set forth inthe examples.

apparent to those skilled in the art, a. widejvariety;

is formed in a comparatively large amount. the sludge may be still active. In continuous operation, these active sludges may be recycled to the reactors for better utilization of the catalyst.

A Thefollowing detailed examples are for the purpose of illustrating modes of carrying out the process of our invention, it being clearly under stood that the invention is not to be considered as 'limited to thespecic manipulation and'condl- As "it will be of. other' heterocyclic compounds within the 4scope of our invention may beused as inhibitors.

- Example 1 tane,y 0.86 part by weight of pure thiopheneVand 16.1 parts by weight of aluminum turnings9 was charged into .a stirring autoclave. 6.9 partsrby weight of dry, gaseous hydrogen chloride were added and then the yautoclave was heated to a temperature oi 100 C. and maintained at about this temperaturefor one hour. The autoclave wasthen cooled for about ten minutes in ice-a water and any residual gas was released slowly through a soda-lime tube which scrubbed outauy remaining hydrogen chloride. This gas `was sub Sequently passed through a trap maintained at low temperatures with a dry ice-acetone cooling mixture.V Only traces of a liquid, identified as pentaneawere .carried ,out by the hydrogen ohiom ride. The synthetic crude. remaining Vin the autoclave was Water-Washed, and then alkaliwashed until all acid-had beenremoved from the hydrocarbon mixture. Finally. the synthetic crude was dried over calcium chloride and analyzed by Podbielniak distillation with the following results:

y Example 2 The run'descr-bed in Example 1 was repeated out in this case, the-0.86 part by weight of thiophene was replaced by 1.69 parts by VWeight of pyridine hydrochloride. The synthetic crude analyzed as follows: v

A Per cent by weight isopentane 23.3

Normal pentane 69.7

Residue Emmole 3 The run described ln Example 1 was repeated but in this case, the 0.86 part by weight of thiophene was replaced by 1.1 parts by weight of piperidine. The synthetic crude analyzed asiellows: l l

Per cent by Weight llsopentane 1a.@ .'{sobutane ,1 `elor'mal pentane 77.0 6.6

Residue y y l5 A mixture containing 94.7 parts by Weight of normal pentane, 5.3 parts by weight of cyclobenaccesos Example 4 The run described in Example 1 was repeated but in this case, the 0.86 part by Weight of thio- .phene was replaced by 2.74 parts by weight of quinolineand the charge contained'99-4 parts by weight of normal pentane and 0.6 part by weight of cyclopentane.

as-follows: Y

Per cent by Weight vIsopentane 6.8 Isobutane" 1.1 Normal nentane 36.8 Residue *53 F:-.It`:z:ample 5 c 'l The run described lin Example l. was repeated but in this case, the 0.36 part by weight of thiophene was replaced by 2.15 parts by weight -o a-plcoline and the charge contained 100 parts by weight ofV normal pentane. The syntheticy crude analyzed as follows: A l 1 er cent loyweght lsopentane- 15.3

Eutanes 5.4

Normal pentarle 75.3

Residue 4.0

' y :Example of l v The run described in xample 1 was repeated Abut in=this case,l thecharge Was 100 parts by weight' of normal hexane, 0.82 part byfweight of pure thophene, 15.4 parts by weight of `aluminum turnings, and 9.5- parts by weight of dry, gaseous 2,2-olimethy1"butane ci 3 Z-dimethyl butane 3 V.'2-.nxethyl pentane er 3 3=1Ioethyll pentane A I-. 1 0: 3

Normal hexane. YZ0-:e110 Residue 1.8

' would analyze as follows:

hydrogen chloride. The synthetic crude analyzed asiollows :f n Vv l .Per cent by weight AYButanes and.pentanes Trace in the absence of thlophene, the synthetic crude Per cent by Weight Butanes and pentanes l? 2,2dimethyl butane Il 2,3-dimethyl rbutane 4 2-methy1 `pentane 6 lll-methyl pentane 2 Normal hexane 23 'Residue n--- 14 Example 7 The run described in Example l was repeated l "out in this case, `the charge was parts by vweight of pure normal heptane, 14.5 parts by weight of aluminum turnings, 9.4 parts by weight of dry, gaseous' hydrogen chloride, and 7.94 parts by weight of pyridine hydrochloride. The reaction mixture was main-tained at about 100 C.

' for about 2 hours. The synthetic crude analyzed as follows: j

Y .Per cent by weight Butanes and'pentanes 2L3f-dirnethylpentane Trace '2-methylhexane 312 'l-snethyihexane 1 5i2 Normal heptane 76:25

Residue The synthetic crude analyzed l1 In the absence ofpyridine hydrochloride, the synthetic crude would analyze as follows:

Per cent by weight Butanes and pentanes 30 Although the present invention has been described in conjunction with preferred embodij ments, it is to be understood that modifications and variations may be resorted to without departing from the spirit and scope ofl the invention, as those skilled in the art will readily understand. Such variations and modications are considered to be within the purview and scope of the appended claims. f

We claim:

l. In the process which involves subjecting a heptane to an isomerization reaction, which includes contacting said heptane in a reaction zone under isomerization reaction conditions, with nascent aluminum chloride isomerization catalyst formed in said reaction zone under said isomerization reaction conditions; the improvement which comprises effecting said isomerization req action in the presence of thiophene. in amounts permitting the isomerization reaction and sumcient to materially suppress side reactions.

2. The process for eecting the isomerization of a hexane, which comprises contacting said hexane in a reaction zone under isomerization reaction conditions, with nascent aluminum chloride isomerization catalyst formed in said reaction zone under said isomerization reaction conditions, in the presence of thiophene, in amounts permitting the isomerizatin reaction and suicient to substantially completely inhibit side reactions.

3. The process for effecting the isomerization of a pentane, which comprises contacting said pentane in a reaction zone under isomerization reaction conditions, with nascent aluminum chloride isomerization catalyst formed in. said reaction zone under said isomerization reaction conditions, in the presence of thiophene, in amounts permitting the isomerization reaction and suiicient to substantially completely inhibit side reactions.

4. The process for effecting the isomerization of a paraiiinic hydrocarbon having ve to seven carbon atoms inclusive, which comprises contacting said hydrocarbon in a reaction zonev under isomerization reaction conditions, with a nascent aluminum halide isomerization catalyst formed in said reaction zone under said isomerization reaction conditions, in the presence of thiophene, in amounts permitting the isomerlzation reaction and suiiicient to materially suppress side reactions.

5. The process for eiecting the isomeriration of a heptane, which comprises contacting said heptane in a reaction zone under isomerization reaction conditions, with nascent aluminum chloride isomerization catalyst formed `in said reaction zone under said isomerization reaction conditions, in the presence of material selected from the group consisting of thiophene, furfuraldehyde, furan. pyridine, piperidine, a-picoline. carbazole, indole, and quinoline, in amounts per-` mitting the isomerization reaction and suiilcient to materially suppress side reactions.

6. The process for eilecting the isomerization 12 oi a hexane, which comprises contacting said hexane in a reaction zone under isomerization reaction conditions, with nascent aluminum chloride isomerization catalyst formed in said reaction zone under said isomerization reaction conditions, in the presence of material selected from the group consisting of thiophene, furfuraldehyde, furan, pyridine, plperidine, a-picoline, carbazoie, indole, and quinoline, in amounts permitting the isomerization reaction and suiiicient to substantially completely inhibit side reactions. 7. In the process which involves subjecting a pentane to an isomerization reaction, which includescontacting said pentane in a reaction zone under isomerization reaction conditions, with nascent aluminum chloride isomerization catalyst formed in said reaction zone under said isomerization reaction conditions; the improvement which comprises effecting said isomerization reaction in the presence of material selected from the group consisting of thiophene, furfuraldehyde. furan, pyridine, piperidine, epicoline, carbasole, indole, and quinoline, in amounts permitting the isomerization reaction and sunicient to substantially completely inhibit side reactions.

8. In the process which involves subjecting a paraiiinic hydrocarbon having five to seven carbon atoms inclusive, to an isomerization reaction. which includes contacting said hydrocarbon in a reaction zone under isomerization reaction conditions, with a nascent aluminum halide isomerization catalyst formed in said reaction zone under said isomerization reaction conditions; the improvement 'which comprises eiecting' said isomerization reaction in the presence of material selected from the group consisting of thiophene, furfuraldehyde, furan, pyridine, piperidine, a-picoline, carbazole, indole, and quinoline, in amounts permitting the iscmerization reaction and suilicient to materially suppress side reactions.

9. The process for eiecting the isomerizatlon of n heptane, which comprises contacting said heptane in a reaction zone under isomerization reaction conditions, with nascent aluminum chloride isomerization catalyst formed in said reaction zone under said isomerization reaction conditions, in the presence of pyridine, in amounts permitting the isomerization reaction and suiilcient to materially suppress side reactions. l,

10. In the/process which involves subjecting a hexane to an somerization reaction, which iricludes contacting said hexane in a reaction zone under lsomerizatlon reaction conditions, with nascent aluminum chloride isomerization catalyst formed in said reaction zone under said isomerization reaction conditions; the improvement which comprises eiecting said isomerlzation reaction in the presence l of pyridine, in

amounts permitting the isomerization reaction and sullcient to substantially completely inhibit side reactions.

il. The process for eiecting the isomerization of` a pentane, which comprises contacting said pentane in a reaction zone under isomerization reaction conditions, with nascent aluminum chloride isomerization catalyst formed in said reaction zone under said isomerization reaction conditions, in the presence of pyridine, in amounts permitting the isomerization reaction and sufficient to substantially completely inhibit side reactions.

12. The process for effecting the isomerization of a paralnic hydrocarbon hating ve to seven carbon atoms inclusive, which comprises con- *A tasting said hydrocarbon in a reaction zone under isomerization reaction conditions, with a REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date Crawford et al Dec. 14, 1943 Laughlin Mar. 14, 1944 Reeves Mar. 14, 1944 

